docs: def CMS_label(text="Preliminary 2012", sqrts=8, pad=None):
      """ Add a 'CMS Preliminary' style label to the current Pad.
  
      The blurbs are drawn in the top margin.  The label "CMS " + text is drawn
      in the upper left.  If sqrts is None, it will be omitted.  Otherwise, it
      will be drawn in the upper right.
      """
      if pad is None:
          pad = ROOT.gPad
      with preserve_current_canvas():
          pad.cd()
          left_margin = pad.GetLeftMargin()
          top_margin = pad.GetTopMargin()
          ypos = 1 - top_margin / 2.
          l = ROOT.TLatex(left_margin, ypos, "CMS " + text)
          l.SetTextAlign(12) # left-middle
          l.SetNDC()
          # The text is 90% as tall as the margin it lives in.
          l.SetTextSize(0.90 * top_margin)
          l.Draw()
          keepalive(pad, l)
          # Draw sqrt(s) label, if desired
          if sqrts:
              right_margin = pad.GetRightMargin()
              p = ROOT.TLatex(1 - right_margin, ypos,
                              "#sqrt{{s}}={0:d}TeV".format(sqrts))
              p.SetTextAlign(32) # right-middle
              p.SetNDC()
              p.SetTextSize(0.90 * top_margin)
              p.Draw()
              keepalive(pad, p)
          else:
              p = None
          pad.Modified()
          pad.Update()
      return l, p